摘要:

The catalytic decomposition of ozone on an α-Fe2O3catalyst has been investigated within the temperature range 23-65°C. A high initial decomposition degree followed by a decrease is observed. It is found that the water vapor in the air-ozone mixture exercises almost no effect on the process. IR-spectroscopy has shown that the nitrogen oxides formed in the ozone generator are the main reason for the deactivation of the catalyst. A scheme of the deactivation process is proposed.

ISSN:0191-9512    

DOI:10.1080/01919519208552273

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Rate constants for the degradation of five herbicides (Mecoprop, MCPA, 2,4-D, Simazine and Atrazine) by ozone were determined in the laboratory under controlled conditions at both acidic and neutral pH using a competition kinetic method. The order of herbicide degradation rate was found to be as follows: Mecoprop > MCPA > 2,4-D > Simazine > Atrazine, both at pH 2 and pH 7.5. The half-life times for herbicide removal at pH 7.5 and in the presence of bicarbonate ions are, respectively, 25.9; 27.5; 39.5; 66.6 and 94.2 minutes for Mecoprop, MCPA, 2,4-D, Simazine and Atrazine at a dissolved ozone concentration of 10 μM. The kinetics of ozone consumption for the three phenoxyalkyl acid derivatives were investigated at pH 2. The study has demonstrated that at neutral pH the initial concentration ratio of two herbicides in solution together did not affect their relative degradation rate.

ISSN:0191-9512    

DOI:10.1080/01919519208552274

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Kinetic studies of the ozonation of two wastewaters released by distillery and tomato processing plants have been carried out. Once it has been assumed that an irreversible gas-liquid reaction is developed between ozone and the matter present in the water, the film theory concept was applied to this system for kinetic determinations. The evolution of the organic and inorganic matter with ozonation time has been followed by the chemical oxygen demand. The procedure allows the determination of the rate coefficients of ozone with the wastewaters treated. According to the results obtained, ozone is consumed through fast reactions which take place near the water-gas interface during an initial period. This period is used to determine the rate coefficients. Then, at more advanced ozonation times, the reactions become slower and hence they take place in the bulk of the water, articularly for the case of tomato wastewaters. Values of the rate coefficient allow us to establish both the kinetic regime of absorption and to compare the reactivity of ozone with the wastewaters and single compounds.

ISSN:0191-9512    

DOI:10.1080/01919519208552275

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Proposed uses of ozone for stand-alone cooling water treatment raise critical questions as to what happens chemically. These questions are of more significance to industrial cooling water systems, which typically have higher temperatures and cooling ranges than do comfort cooling systems. When applying ozone to cooling waters, it is very important for the user to understand many fundamental aspects of ozone chemistry. For example, when ozone is added at water pH levels often encountered in cooling waters (≥ 8), it decomposes to form hydroxyl free radicals, which are stronger oxidizing agents than molecular ozone itself, but of microsecond half-life, and therefore are poor disinfectants. The presence of bicarbonate alkalinity, hardness, naturally occurring organics, bromide ion, and effects of pH levels on water quality parameters and molecular ozone, have pronounced effects on chemical reactions which occur when ozone is added to cooling waters. The authors review the fundamental chemistries involved with ozone in water, discuss the effects of water constituents present or expected to be present in recycling cooling waters, relate these aspects to biocidal efficacy of ozone treatment, and explore possible mechanisms for scale and corrosion control in cooling systems by ozone.

ISSN:0191-9512    

DOI:10.1080/01919519208552276

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

ISSN:0191-9512    

DOI:10.1080/01919519208552272

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor